Greek socialist leader George Papandreou, the apparent winner of Sunday's national election, has told supporters he plans to lead the country on a course of recovery, development and creation.

Mr. Papandreou, the son and grandson of former prime ministers, has promised a $4.4 billion stimulus package to revive the national economy.

U.S. President Barack Obama called Mr. Papandreou Sunday to congratulate him on his victory. Mr. Obama said he looks forward to working with the new Greek leader. The president also sent well-wishes to all Greeks who participated in the vote.

Conservative Prime Minister Costas Karamanlis conceded defeat and resigned as head of his New Democracy Party after early results showed the opposition Socialist (PASOK) party more than seven percent ahead.

With most of the ballots counted, an official projection put the Socialists at about 43 percent of the vote and the conservatives at about 34 percent. Final results are expected Monday.

The Interior Ministry says the Socialists could win up to 160 seats in the 300-member parliament.

Prime Minister Karamanlis ordered the election halfway through his term, saying Greece needs a government with a clear mandate to deal with its economic woes.

The country's ruling party has been stung by corruption scandals and voter discontent with the economy.

Conservatives once loyal to Mr. Karamanlis also criticized the government's handling of riots late last year, triggered by the fatal police shooting of an Athens teenager.